The invention relates to a process for pledging data for a secure data-exchange protocol.
The invention applies especially, advantageously, to physical and logical access control systems, for example in computer networks or checking systems such as those found for example in decoders for conditional-access television (pay television, encoded television, etc.). Of course, these applications are in no sense limiting and are given here merely by way of examples of technical fields in which the invention may be used.
The principle of pledging a data item consists, for a first party, in committing a predetermined data item to another party but without communicating this data item in clear. During a subsequent step, the first party reveals the plain data item to the second party, the latter having the possibility of verifying at this time that the plain data item is indeed that which had been secretly pledged beforehand.
Here and in what follows it will be noted that the term "party" relates equally to moral or physical persons as to electronic or computer systems exchanging data between themselves in an entirely automatic manner in the framework of a particular protocol, or, more generally, of a given transaction.
Similarly, the data item forming the subject of the transaction will be referred to as the "pledged data item", the party who initially holds the pledged data item (the "first party" indicated above) will be referred to as the "debtor" and the party for whom the pledged data item is intended (the "second party" indicated above) will be referred to as the "creditor".